Let's say USC, Oregon, UW, UCLA leave to go to the Big 10. 4 teams that have exponentially more resources, money and prestige than Utah does currently, leave.
From a W/L perspective, this is very beneficial to Utah.
Now Utah only plays teams with similar resources or less, just like the old MW but with more prestige, as the Pac-12 gets some arrangement of Big 12 and upper tier MWC schools to form a new conference.
But none of these schools have been nearly as successful as Utah the last 5-6 years. They don't have the program and coaching stability, recruiting momentum, NFL pipeline, etc.
And they are not going to have any resource advantages over Utah.
Utah would be consistently at the top, a perennial playoff contender and one of the top performing non blue blood programs in the country.